CN100401912C - Slowly digestible starch products - Google Patents

Abstract

The present invention relates to a slowly digestible starch prepared by debranching amylose-containing starch, especially by pullulanase or isoamylase. These slowly digestible starches can be used in edible products, including nutritional supplements.

Description

Slowly digestible starch products

technical field

The present invention relates to a slowly digestible starch product produced by enzymatic debranching of amylose-containing starch and crystallization of the resulting linear chains into a highly crystalline form.

Background technique

Starches are the main source of energy in the typical American diet. Refined starches are primarily eaten cooked, and this form generally has a high diabetic index and is digested essentially rapidly. Some refined starches are resistant to enzymatic hydrolysis in the small intestine, these starches are essentially not broken down until it reaches the large intestine where it is utilized by parasitic microorganisms (resistant starch).

A need has been recognized for a slowly digestible starch which provides glucose to the consumer over an extended period of time. These slowly digestible starches are therefore useful in food and pharmaceutical applications.

These slowly digestible starches are used as excellent carbohydrates in foods, including medical foods and nutritional supplements, for diabetic and pre-diabetic individuals. These slowly digestible starches can also be used in healthy individuals who wish to moderate their glucose response or obtain sustained energy release through food consumption.

Research literature suggests a role for slowly digestible starches in health, as glucose is released over an extended period of time. Research suggests that health-related benefits may include increased satiety over a longer period of time (ie, for weight control), sustained energy release (ie, for increased motor performance, including training), and increased focus on maintenance and memory improvement.

These slowly digestible starches can also be used as medicines, for example to reduce the risk of diabetes. In addition, slowly digestible starches are useful in the treatment of hyperglycemia, insulin resistance, hyperinsulinemia, dyslipidemia, and abnormal fibrinolysis. It can also be used to treat obesity.

It has now surprisingly been found that a slowly digestible starch can be produced by enzymatic debranching of amylose-containing starch to give a mixture of long and short linear chains.

Contents of the invention

This patent relates to a slowly digestible starch product made by debranching amylose-containing starch and crystallizing the resulting highly linear amylose into a highly crystalline form. This slowly digestible starch provides sustained energy release with a low diabetic index.

The term "rapidly digestible starch" as used herein refers to starch or fractions thereof which are digested within a digestion period of 20 minutes, as described for example by Englyst et al., 1992 (Englst et al., European Journal of Clinical Nutrition, 1992, 46, S33 -S50) determination.

The term "resistant starch" as used herein refers to starch, or fractions thereof, that is not digested in the small intestine, for example as determined by Englyst et al., 1992 (Englyst et al., Eur. J. Clin. Nutrition, 1992, 46, S33-S50).

As used herein, the term "slowly digestible starch" refers to starch or fractions thereof that are not rapidly digestible starch or resistant starch.

As used herein, "totally or completely debranched starch" refers to a starch which theoretically contains 100% by weight linear chains, but which is, in practice, so highly debranched that other enzymatic activities no longer produce a measurable change in the percentage of linear chains .

"Diabetes index" as used herein refers to the increased area under the glycemic response curve for a 50 g carbohydrate portion of a test food, expressed as a percentage of the response relative to the same amount of carbohydrates of a standard food ingested by the same subjects. Typically, carbohydrates are on an available basis and white bread or dextrose are used as standard foods. See Carbohydrates in Human Nutrition, FAO Food and Nutrition Bulletin 66, Report of the Joint FAO/WHO Expert Consultation, Rome, 14-18 April 1997.

Detailed ways

This patent relates to a slowly digestible starch product produced by enzymatic debranching of amylose-containing starch and crystallization of the resulting linear chains into a highly crystalline form. This slowly digestible starch provides sustained energy release with a low diabetic index.

"Starch" as used herein includes all starches derived from any natural source, which are suitable for use herein. Native starch as used herein is a starch that exists in nature. Also suitable are starches derived from plants (including variations thereof) obtained by standard breeding techniques, including crossing, translocation, inversion, transformation or any other method of genetic or chromosomal engineering. In addition, starches derived from artificially mutated and mutated grown plants of the above general composition made by known standard mutagenesis breeding methods are also suitable for use herein.

Typical sources of starch are cereals, tubers, roots, legumes and fruits. The natural source may be any amylose-containing variety of corn (maize), pea, potato, sweet potato, banana, barley, wheat, rice, oats, sago, amaranth, cassava, arrowroot, canna, sorghum, and other High amylose variety. As used herein, the term "amylose-containing" includes starches containing at least about 10% by weight amylose. As used herein, the term "high amylose" includes starches comprising at least about 40%, especially at least about 70%, more especially at least about 80% by weight amylose. Especially suitable are starches that are not high amylose (ie, from about 10 to about 40% by weight amylose).

The starch is debranched enzymatically using techniques known in the art. Suitable enzymes are endo-alpha-1,6-D-glucanohydrolases, especially pullulanases and isoamylases, more especially isoamylases.

The amount of enzyme used depends on the source and activity of the enzyme and the substrate used. For example, if an isoamylase is used, typically the enzyme is present in an amount of about 0.05 to about 10%, especially about 0.2 to about 5%, by weight of the starch.

Optimal parameters for enzyme activity vary depending on the enzyme used. The rate of enzymatic degradation depends on several factors known in the art, including enzyme type and concentration, substrate concentration, pH, temperature, the presence or absence of inhibitors, and the degree and type of modification, if any. These parameters can be adjusted to optimize the rate of digestion of the starch matrix.

The starch is gelled using techniques known in the art prior to enzymatic debranching. Techniques known in the art include, for example, those disclosed in US Patent Nos. 4,465,702, 5,037,929, 5,131,953 and 5,149,799. See also, Chapter XXII - "Production and Use of Pregelatinized Starch", Starch: Chemistry and Technology, Volume III - Industrial Aspects, edited by R.L. Whistler and E.F. Paschall, Academic Press, New York 1967. The gelatinization process unfolds the starch molecules from a granular structure, which allows enzymes to degrade the starch molecules more easily and uniformly.

Generally, the enzyme treatment is carried out in an aqueous or buffered slurry at a starch solids content of from about 10 to about 40%, depending on the base starch being treated. In the present invention, a solids content of about 15-35% is especially useful, and about 18-30% is more especially useful. Alternatively, the process may employ enzymes immobilized on supports.

Typically, enzymatic hydrolysis is carried out at the highest feasible solids content without reducing the reaction rate to facilitate any desired subsequent drying of the starch composition. The reaction rate can be reduced by high solids content as agitation becomes difficult or ineffective and the starch dispersion becomes more difficult to handle.

The pH and temperature of the slurry should be adjusted to provide efficient enzymatic hydrolysis. These parameters depend on the enzyme to be used and are known in the art. For example, if an isoamylase is used, the temperature is usually about 25 to about 70°C, especially about 50 to about 60°C. The pH is generally adjusted to about 4.5 to about 6.5, especially about 5.0 to about 6.0, using techniques known in the art.

The enzymatic reaction continues until slowly digestible starch is obtained. Generally, the enzymatic reaction takes about 1 to about 24 hours, especially about 4 to about 12 hours. The reaction time depends on the type of starch used, the type and amount of enzyme used, and the reaction parameters of % solids, pH and temperature.

The amount of hydrolysis can be monitored and determined by measuring the concentration of reducing groups released by alpha-1,6-D-glucanohydrolase activity by methods well known in the art. Reaction endpoints can be determined using other techniques such as monitoring changes in viscosity, iodine reactions, or changes in molecular weight. If the starch is completely debranched, the monitored measurements will no longer change. The starch can be debranched to any extent, especially at least about 90%, more especially at least about 95%.

Enzymes can be deactivated (denatured) by any technique known in the art, such as heat, acid or base deactivation, if desired. For example, acid deactivation can be achieved by adjusting the pH to below 3.0 for at least 30 minutes, or thermal deactivation can be achieved by raising the temperature to about 80 to about 90° C. and maintaining it at that temperature for at least about 20 minutes. Complete deactivation of the enzyme is achieved.

Starch can also be further modified before or after enzymatic hydrolysis. These modifications can be physical, enzymatic, or chemical modifications. Physical modification includes shear or heat-inhibition, such as the process described in US Patent 5,725,676.

Chemical modifications include, but are not limited to, crosslinking, acetylation and organic esterification, hydroxyalkylation, phosphorylation and inorganic esterification, cationic, anionic, nonionic, and zwitterionic modifications, and succinylation. Such modifications are known in the art, eg, Modified Starches: Properties and Uses, edited by Wurzburg, CRC Press, Inc. Florida (1986).

Starches are convertible and are meant to include flowable or thin-boiling starches made by oxidation, acid hydrolysis, enzymatic hydrolysis, heat and/or acid dextrinization. These processes are well known in the art.

Any base starch having properties suitable for use herein may be purified by any method known in the art to remove aromas and colors inherent in the polysaccharides of the starch or developed during processing. A purification process suitable for the treatment of starch is disclosed in the patent family denoted EP 554 818 (Kasica, et al.). Alkaline washing techniques are also useful and are described in patent families denoted U.S. 4,477,480 (Seidel) and 5,187,272 (Bertalan et al.). Debranched starch can also be purified using this method.

The resulting solution is typically adjusted to the desired pH depending on its intended end use. Generally, the pH is adjusted to about 5.0 to about 7.5, especially about 6.0 to about 7.0, using techniques known in the art. In addition, any linear chains that precipitate out of the starch dispersion can be redispersed. If purification of the demyelinated starch composition is desired, reaction impurities and by-products can be removed by dialysis, filtration, centrifugation or any other method known in the art for isolating and concentrating starch compositions. For example, degraded starch can be washed using techniques known in the art to remove soluble low molecular weight fractions such as oligosaccharides, resulting in a more highly crystalline starch.

Debranched starch is crystallized by methods known in the art, for example by allowing the starch to stand and age. The starch is then recovered using methods known in the art, especially by filtration or by drying, including spray drying, freeze drying, flash drying or air drying, more particularly by filtration or flash drying. It is important to control crystallization, usually by controlled aging and drying, to obtain the necessary degree of crystallinity important to the present invention. It is further important that drying methods and other post-crystallization processes do not substantially damage the crystals.

The resulting starch is in the form of highly crystalline linear alpha-glucans from debranched starch and is uniquely used as slowly digestible starch. The starch is characterized by a melting point temperature Tp of at least about 70°C, especially at least about 80°C; more particularly at least about 90°C, as determined by DSC using the procedure described below, and an enthalpy ΔH of at least about 25 J/g as determined by DSC using the procedure described below , especially at least about 30 J/g. These DSC values indicate the highly crystalline nature of the product.

The resulting starch is slowly digestible in that it has continuous digestion especially over a period of at least 2 hours, more particularly over a period of at least 4 hours, being still significantly digested at about 6 hours after ingestion. In particular, less than about 50%, most especially less than about 30%, is digested within the first 20 minutes after consumption, and at least about 20%, especially at least about 30%, is digested between 20 minutes and 2 hours after consumption Digestion, which was determined using the digestion procedure described below. Additionally, at least about 50%, especially at least about 60%, is digested within 2 hours of consumption.

Starch can be consumed in its raw state, but is usually consumed after processing under high or low moisture conditions. Thus, the present invention includes those starches that are slowly digested in the state in which they are consumed. These states were modeled by the methods described in the Examples below.

In addition, the resulting slowly digestible starches do not produce the large, rapid increases in blood glucose levels that are common with high-diabetic index starches, but instead provide a more modest increase above baseline that lasts for a longer period of time. Additionally the process allows that the slowly digestible fraction is not substantially reduced by cooking and/or other typical food handling conditions.

Starches are used in a variety of edible products including, but not limited to: cereals, bars, pizza, pasta, dressings, including pourable and spoonable dressings; pie fillings, including fruit and cream Massecuite fillings; sauces, including white sauces and dairy-based sauces such as cheese sauces; gravies; light syrups; puddings; custards; yogurt; sour cream; beverages, including dairy-based beverages; icings; baked goods , including crackers, breads, muffins, bagels, biscuits, cookies, pie crust and cakes; condiments, candies and gum, and soups.

Edible products are also meant to include nutritional foods and beverages, including nutritional supplements, diabetic products, products for sustained energy release such as sports drinks, nutritional bars and energy bars.

The starches of the present invention may be added in any desired amount to achieve the functionality of the composition. Generally, starch may be added in an amount of about 0.01% to about 100%, especially about 1% to about 50%, by weight of the composition. Starch can be added to food or beverages in the same manner as any other starch, usually by mixing directly into the product or adding it as a sol.

The embodiments given below serve to further illustrate the invention and should not be construed as limiting in any respect.

Embodiment 1. A starch composition made from amylose-containing starch comprising crystalline linear alpha-glucan, characterized in that:

a) at least about 20% slowly digestible starch;

b) less than about 50% rapidly digestible starch;

c) a melting point temperature Tp of at least about 70°C as determined by DSC; and

d) An enthalpy, ΔH, as determined by DSC of at least about 25 J/g.

Embodiment 2. The starch composition of embodiment 1, wherein at least about 50% is digested within a 2 hour digestion period.

Embodiment 3. The starch composition of embodiment 1, wherein at least about 60% is digested within a 2 hour digestion period.

Embodiment 4. The starch composition of embodiment 1, wherein the starch composition is made from a starch selected from maize starch, sago starch, tapioca starch and potato starch.

Embodiment 5. The starch composition of embodiment 1, wherein the melting point temperature is at least about 80°C.

Embodiment 6. The starch composition of embodiment 1, wherein the melting point temperature is at least about 90°C.

Embodiment 7. The starch composition of embodiment 1, wherein the enthalpy is at least about 30 J/g.

Embodiment 8. The starch composition of embodiment 1, characterized by at least about 30% slowly digestible starch.

Embodiment 9. A process for manufacturing the starch composition of embodiment 1, comprising:

a) debranched amylose-containing starch;

b) crystallizing amylopectin; and

c) drying the highly crystalline debranched starch.

Embodiment 10. The process of embodiment 9, wherein the starch composition is debranched using pullulanase or isoamylase.

Embodiment 11. An edible product comprising the starch composition of embodiment 1.

Embodiment 12. The product of Embodiment 11, wherein the product is a nutraceutical.

Embodiment 13. The starch composition of any one of embodiments 1-3, wherein the starch composition is made from a starch selected from the group consisting of maize starch, sago starch, tapioca starch, and potato starch.

Embodiment 14. The starch composition of any one of Embodiments 1-4 or 13, wherein the melting point temperature is at least about 80°C.

Embodiment 15. The starch composition of embodiment 14, wherein the melting point temperature is at least about 90°C.

Embodiment 16. The starch composition of any one of embodiments 1-6 or 13-15, wherein the enthalpy is at least about 30 J/g.

Embodiment 17. The starch composition of any one of Embodiments 1-7 or 13-16, characterized by at least about 30% slowly digestible starch.

Embodiment 18. A process for making the starch composition of any one of embodiments 1-8 or 13-17, comprising:

a) debranched amylose-containing starch;

b) crystallizing amylopectin; and

c) drying the highly crystalline debranched starch.

Embodiment 19. The process of Embodiment 18, wherein the starch composition is debranched using pullulanase or isoamylase.

Embodiment 20. An edible product comprising the starch composition of any one of embodiments 1-8 or 13-17.

Embodiment 21. The product of Embodiment 20, wherein the product is a nutraceutical.

Example

The examples given below serve to further illustrate and explain the present invention and should not be construed as limiting in any respect. All % used are by weight.

The following experimental procedures were used throughout the examples:

Differential Scanning Calorimetry - Differential Scanning Calorimetry measurements were performed in a Perkin-Elmer DSC-7 (Norwalk, CT, USA). The instrument is calibrated using indium. A starch sample of about 10 mg at a starch:water ratio of 1:3 was prepared and heated from 5°C to 160°C at 10°C/min. Use an empty stainless steel pan as a reference.

Dextrose Equivalent (DE) - For DE measurements during production, the Fehling volumetric titration method was used. The 500ml Erlenmeyer flask was rinsed with deionized (D.I.) water. Then 50ml of D.I. water was added. 5 ml each of Fehling's solutions A and B, 2 drops of methylene blue were added, followed by two boiling chips. After determining the reaction solids content using a refractometer, a starch solution containing 2-4% starch solids was made by diluting the reaction solution in a beaker using D.I. water. Before proceeding to the next step, the solids content was checked by refractometer to ensure that the solution was prepared correctly. Weigh the beaker containing the starch solution and record the weight. 15 grams of the starch solution was added to the Erlenmeyer flask containing the prepared Fehlings solution. A blue tinge usually develops after they are boiled for 2 minutes on a hot plate with stirring. The starch solution from the beaker was added gradually using a pipette until the blue tint disappeared and the distinctive reddish copper oxide formed. The starch solution was stirred continuously with a plastic pipette to keep the solution homogeneous. When the reddish endpoint was reached, the beaker containing the starch solution was weighed again to determine the weight of starch consumed. The calculation of D.E. can be seen from the following formula:

D.E.=[Fehling factor X100]/[(grams required for starch solution) x (concentration of starch solution)]

Simulated digestion - (Englyst et al., European Journal of Clinical Nutrition, 1992, 46, S33-S50) - food samples were ground/chopped as if chewed. Powdered starch samples were sieved to a particle size of 250 microns or less. Weigh out 500-600 mg ± 0.1 mg sample and add to sample tube. 10 ml of pepsin (0.5%), guar gum (0.5%), and HCl (0.05 M) solution were added to each tube.

Blank and glucose standard tubes were prepared. The blank was 20ml of buffer containing 025M sodium acetate and 0.02% calcium chloride. Glucose standards were prepared by mixing 10 ml of sodium acetate buffer (described above) and 10 ml of 50 mg/ml glucose solution. Standards were made in duplicate.

The enzyme mix was prepared by adding 18 g of porcine pancreatin (Sigma P-7545) to 120 ml of deionized water, mixing well, followed by centrifugation at 3000 g for 10 minutes. The supernatant was collected and 48 mg dry invertase (Sigma 1-4504) and 0.5 ml AMG 400 (Novo Nordisk) were added.

The sample tubes were pre-incubated for 30 minutes at 37°C, then removed from the bath and 10 ml of sodium acetate buffer was added along with glass balls/marbles (used to aid in physical breakdown of the samples during shaking).

Add 5ml of enzyme mix to samples, blanks, and standards. Tubes were shaken horizontally at approximately 180 strokes/min in a 37°C water bath. Time "zero" indicates the first addition of the enzyme mix to the first tube.

After 20 and 120 minutes, 0.5 ml aliquots were removed from the incubated samples and placed in another tube of 20 ml 66% ethanol (to stop the reaction). After 1 hour, aliquots were centrifuged at 3000g for 10 minutes.

The glucose concentration in each tube was determined using the glucose oxidase/peroxidase method (Megazyme glucose assay procedure GLC9/96). This is a colorimetric step. HPLC can also be used to detect glucose as described in earlier literature using this assay.

Starch digestibility was determined by calculating glucose concentration relative to glucose standards using a conversion factor of 0.9. Results are taken as "% starch digested" (dry weight basis) after 20 and 120 minutes. SDS (Slowly Digestible Starch) is the 120 minute value minus the 20 minute value.

Each sample analysis batch included a reference sample of uncooked cornstarch. The accepted % digestibility ranges for cornstarch are:

sample s20 s120 SDS   Corn starch ¹ 17.5±2.5 80±5 About 62.5

淀粉，购自National Starch and Chemical Company，Bridgewater，NJ，USA。 ^1Melogel

Starch was purchased from National Starch and Chemical Company, Bridgewater, NJ, USA.

Cooking Models - Simulate industrial food processes using two general models: High Moisture; and Low Moisture. The high moisture food model used starch at 20% solids in water which was cooked in a steam bath at 90°C for 5 minutes. The cooks were then frozen in a dry ice/acetone bath, lyophilized, comminuted, and tested for digestion. The low moisture food model used 50% solids starch in water and the paste was baked in an oven at 190°C for about 20 minutes. The cooked starch was ground and sieved to 250 microns or less and then tested for starch digestion profile.

Example 1 - Preparation of debranched and crystallized tapioca and sago starches for digestion studies

A. Slurry 3kg tapioca starch in 8423g water. The pH of the sample was adjusted to 5.5 using 3:1 water:HCl. Samples were jet cooked and placed in a 59°C water bath. If the sample temperature was 59°C, 5% pullulanase (Promozyme 200L from Novo Nordisk) was added. Samples were debranched overnight (16 hours) and the enzymes were subsequently denatured by heating the samples in a 95°C bath for half an hour. After heating, the samples were placed on a benchtop and crystallized overnight at room temperature with gentle stirring. The product was recovered by spray drying at an inlet temperature of 210°C and an outlet temperature of 116°C. The final D.E. of the sample was 5.3.

B. The method of Example 1A was repeated except that the starch was sago starch. The final D.E. is 4.0.

C. The method of Example 1A was repeated except that the tapioca starch was completely debranched using isoamylase. The reaction temperature was 55°C and the pH was 4.0. 0.2% isoamylase (Hayashibara Inc. Japan) was added. Samples were debranched overnight (16 hours) and then the enzyme was denatured by lowering the pH to 2.0 for 30 minutes. After the pH was adjusted back to 6.0, the product was recovered by spray drying at an inlet temperature of 210°C and an outlet temperature of 116°C.

These samples were also subjected to digestion tests. Samples 1A and 1B were cooked using a low moisture model and sample 1C was left uncooked. The samples were then tested for digestion profile. Table 1 presents the digestion results and calculated SDS content together with raw material DSC data.

Table 1. Digestion results and feedstock DSC for debranched and crystallized tapioca and sago starches

The samples of this example had an SDS content of over 20%.

Claims (5)

1. A starch composition made from gelatinized starch containing 10-40% by weight of amylose, wherein at least 95% of the gelatinized starch is debranched as crystalline linear alpha-glucan, characterized in that: a) at least 20% slowly digestible starch; b) less than 50% rapidly digestible starch; c) a melting point temperature Tp of at least about 70°C as determined by DSC; and d) an enthalpy ΔH as determined by DSC of at least about 25 J/g, At least 50% of it is digested within 2 hours. 2. A method of manufacturing the starch composition of claim 1, comprising: a) debranched amylose-containing starch; b) crystallizing amylopectin; and c) drying the highly crystalline debranched starch. 3. The method of claim 2, wherein the starch composition is debranched using pullulanase or isoamylase. 4. An edible product comprising the starch composition of claim 1. 5. The product of claim 4, wherein the product is a nutraceutical.